1. Field of the Invention
This invention relates generally to an impression material and particularly, to a curable organopolysiloxane putty-like composition which is kept putty-like prior to curing by the action of an internal releasing agent. Once the composition has been cured, it becomes useful as an impression material without impeding an appearance or lowering the dimensional accuracy because of a reduced degree of bleeding of the internal release agent. The term "impression material" used herein is intended to mean one which is used, for example, in the dental field as the imprint of the teeth and surrounding tissues for use as a mold in making dentures, or one which is used to imprint the hand. As a matter of course, the putty-like composition may be applied not only as such an impression material, but also for identification and electric insulation.
2. Description of the Prior Art
A variety of curable organopolysiloxane compositions are known in the art. For impression materials, there have been widely used those compositions which comprise organopolysiloxanes having an alkenyl group and organohydogenpolysiloxanes having a hydrogen atom directly bonded to the silicon atom (.tbd.SiH group) and wherein these siloxane compounds are subjected to addition reaction in the presence of a platinum catalyst.
Putty-like compositions ordinarily used are those which are obtained by internally adding aliphatic hydrocarbon release agents such as, for example, liquid paraffin and white vaseline to the composition of the above type, so that the ingredients do not attach to hands when mixing.
The aliphatic hydrocarbon added as the release agent is allowed to bleed on the putty composition surface prior to curing. This is very advantageous from the viewpoint of handling in that when mixed or kneaded, the putty-like composition does not attach to hands. However, the aliphatic hydrocarbon is caused to gradually bleed out on the surface after the curing, presenting the problems that the appearance of the cured product is worsened and that the size of the cured product after impression differs from that of a matrix.